Structure for reducing the drag of a ship and its application

ABSTRACT

A structure for reducing the drag of a ship and its application thereof is provided. The structure for reducing the drag of a ship includes at least one turbulence generating structure which is installed on the side surface between the widest section and the aft end or on the bottom surface between the deepest portion and the aft end of the ship. The arrangement of the turbulence generating structure can generate turbulence to reduce the drag of the ship, and thereby increase the speed of the ship and/or reduce the ship&#39;s fuel consumption.

1. FIELD OF THE INVENTION

The present invention relates to the structure of a ship and its application thereof for reducing drag of the ship while sailing, and particularly to a ship having a turbulence generating structure on the surface of the hull for generating turbulence to reduce drag of the ship and its application thereof.

2. DESCRIPTION OF RELATED ART

A ship suffers drag while sailing, which slows down the speed of ship. The drag causes not only more fuel consumption, but also wears down the motor and the transmitting mechanism, as well as producing more exhaust gas and increasing the time to complete the voyage. The environmental pollution, extra fuel consumption and time loss to the transportation field are inevitable.

Although the streamlining of the shape of ship's hull is helpful to reduce drag, the effect is still limited. Referring to FIGS. 1A and 1B, a perspective view of a conventional ship sailing in the water is shown. The ship 1 comprises a hull 100. The direction of sailing or heading of the ship 1 is depicted as H. The hull 100 comprises a fore end 11, an aft end 14, a widest section 12 and a deepest portion 13 in between the fore end 11 and the aft end 14. When the ship 1 sails, a relative velocity between the water and the hull 100 occurs. A boundary layer 31 is formed on the surface of the hull 100 while the ship 1 is sailing in the water. The boundary layer 31 appears on both sides and the bottom of the hull 100. The boundary layer 31 moves along simultaneously with the hull 100. The boundary layer 31 grows gradually from the fore to the aft of the ship 1 while sailing, so that the increased cross-section area and accumulated volume weight of drag slows down the speed of the ship 1.

Furthermore, the maximum relative velocity between the hull 100 and the water occurs at the widest section 12, and the minimum relative velocity occurs at the fore end 11 and the separation point 15. The separating point 15 locates between the widest section 12 and the aft end 14 at both sides of the ship 1. Wake 34 appears behind the separation point 15. According to Bernoulli's principle, the pressure is inversely proportional to the velocity of water flow, and therefore the fore end 11 of the ship 1 suffers the maximum pressure, the pressure decreasing gradually to the lowest level at the widest section 12, and then increasing gradually to the maximum at the separation point 15. Therefore, the longitudinal total pressure between the fore end 11 and the widest section 12 is greater than the longitudinal total pressure between the widest section 12 and the aft end 14. The difference in the longitudinal pressure also causes drag on the ship. Accordingly, the aforesaid various kinds of drag are detrimental to the ship's speed.

In order to overcome the drag issue for a ship while sailing, the present invention provides a structure installed on the hull of a ship and the application thereof for reducing the drag of a ship, which comprises a turbulence generating structure with a special design to reduce a thickness of the boundary layer to delay the separation and move the separation point 15 further backwards in order to increase the pressure of the aft part of the hull 100, and thereby reduce the drag when the ship is sailing so as to accordingly increase the speed of the ship as well as reduce the fuel consumption.

SUMMARY OF THE INVENTION

In view of achieving the aforementioned purpose, the present invention provides a structure installed on the hull of a ship and its application for reducing the drag of a ship, which include at least one or a plurality of turbulence generating structures installed on the surface of the hull of the ship to generate a beneficial turbulence that reduces the thickness of the boundary layer on the surface of the hull and thereby delays the separation and increases the pressure of the aft part of the hull to speed up the ship.

The structure for reducing drag of the ship of the present invention comprises at least one turbulence generator. The turbulence generators are installed respectively on both side surfaces of the hull between the widest section and the aft end of the ship.

In another embodiment of the present invention, one or a plurality of turbulence generating structures are installed on the bottom surface of the hull between the deepest portion and the aft end of the ship.

In a preferred embodiment, the structure for reducing the drag of a ship of the present invention comprises a plurality of turbulence generating structures, among which two adjacent turbulence generating structures are arranged in an array with a gap between every two adjacent turbulence generating structures.

In the preferred embodiment of the present invention, the structure for reducing the drag of a ship of the present invention comprises a plurality of turbulence generators, which are arranged in series as a stripe configuration without a gap to fit the particular shape of a ship.

In the preferred embodiment of the present invention, the turbulence generating structure comprises an impact surface facing the incoming flow for colliding with the flow to generate turbulence and a front surface facing the water current.

In the preferred embodiment of the present invention, as the ship sails in water, the turbulence generating structure of the ship has a corresponding velocity with respect to the water, and the impact surface of the turbulence generating structure is at a 60 degrees or less intersection angle with the keel line of the ship.

In another embodiment of the present invention, the impact surface of the turbulence generating structure is parallel or inclined at a zero degree angle relative to the keel line of the ship.

In the preferred embodiment of the present invention, the configuration of the turbulence generating structure is a curved-face rectangle, a slanted-face rectangle, a polygon, a trapezium, a polyhedron, a triangular solid, a cone, a semi-circular solid, a semi cone or any other various configurations.

In the preferred embodiment of the present invention, the turbulence generating structure is adhered, embedded, welded to the surface of the hull or is integrally installed with the hull.

In the preferred embodiment of the present invention, the turbulence generating structure may be made of metal, plastic, wood, bamboo, glass, clay, ceramic or composite materials.

The structure for reducing the drag of a ship and its application according to the present invention comprises a hull and at least one turbulence generating structure. The turbulence generating structure is installed on the side surface between the widest section and aft end of the hull, or on the bottom surface between the deepest portion and the aft end of the ship to generate turbulence, and thereby reduce the drag of the ship.

By installing at least one turbulence generating structure on the surface between the widest section and the aft end or the deepest portion and the aft end of the hull, the at least one turbulence generating structure of the present invention may generate a beneficial turbulence behind the turbulence generating structure to thin the boundary layer, which in turn may delay the separation to reduce the drag of the ship and effectively increase the speed of the ship. Consequently, both fuel consumption and navigation time can be effectively saved.

BRIEF DESCRIPTION OF THE DRAWING

For a more complete understanding of the present invention, reference will now be made to the following detailed description of preferred embodiments taken in conjunction with the following accompanying drawings.

FIGS. 1A and 1B show the water flow diagram of a conventional ship sailing in the water.

FIGS. 2 and 2A illustrates the structure of the turbulence generating structure according to an embodiment of the present invention.

FIG. 3 illustrates the force acting on the turbulence generating structure by the current according to an embodiment of the present invention.

FIG. 4 illustrates a boundary layer in the laminar flow.

FIG. 5 illustrates a boundary layer in the turbulent flow.

FIG. 6 illustrates the stream lines on the underwater surface of a ship when the water flows through the ship.

FIG. 7 illustrates the stream lines behind the turbulence generating structure installed on the underwater surface of the aft part of the hull.

FIG. 7A illustrates an enlarged view of the portion B of FIG. 7.

FIG. 8 illustrates the turbulence generating structure itself which is parallel to L and H, produces minimum drag to navigation.

FIG. 9 illustrates a plurality of turbulence generating structures disposed on a port side or bottom hull surface of the ship.

FIG. 10 illustrates the same turbulence generating structures disposed on the hull of a ship according to the present invention viewed from the port side bottom.

FIG. 11 illustrates the turbulence generating structures disposed on the surface of the bottom of the hull and the turbulence generated by the turbulence generating structures.

FIG. 12 illustrates the turbulence generating structure of the present invention in various configurations, 12(A) is a triangular solid, 12(B) is a curved-face rectangle, 12(C) is a semi-circular solid, 12(D) is a slanted-face rectangle, 12(E) is a polyhedron.

FIG. 13 illustrates the boundary layer according to the present invention.

FIG. 14 illustrates a schematic diagram of the laminar boundary layer being fluctuated by the turbulence generating structure becoming the turbulent boundary layer according to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

In order to lay out the above and other purposes, features and advantages of the present invention more explicitly, the embodiments are described herein with reference to the accompanying drawings.

Referring to FIGS. 2 and 3, the variation and the effects of the current when it encounters the turbulence generating structure of the present invention is described as follows. As shown in FIG. 2 and FIG. 7, a turbulence generating structure 2 installed on the hull 100 of a ship 1 comprises an impact surface 21 facing the incoming flow of water for colliding with and generating turbulence when the flow collides with the impact surface 21. The turbulence generating structure 2 also comprises a front surface 22 with a shape of a slope or curved surface as shown in FIG. 12. When the ship 1 is in the H sailing traveling forward, the front surface 22 of the turbulence generating structure 2 face water current. Since the shape of the front surface 22 is a slope or curved surface, therefore the resistance of the ship 1 is minimized. Current C has a relative velocity with the turbulence generating structure 2 when the ship 1 sails in the water. As shown in FIG. 2, when the current C flows pass through the turbulence generating structure 2 with an attack angle A, more turbulence V will be induced behind the turbulence generating structure 2 when the current C collides with the turbulence generating structure 2, while comparatively less turbulence V is induced with the turbulence generating structure 2 arranged parallel to the flow of the current C. Referring to FIG. 3, when the current C collides with the turbulence generating structure 2, the current C exerts a force F on the impact surface 21 of the turbulence generating structure 2. The force F includes a vertical component Fv perpendicular to the turbulence generating structure 2 and a horizontal component Fh parallel to the turbulence generating structure 2. The component Fv of the force on the turbulence generating structure 2 becomes a thrust force acting on the turbulence generating structure 2. Because the size of the turbulence generating structure 2 is substantially less than the hull 100 of the ship 1, the side thrust exerted on the turbulence generating structure 2 of the component Fv is relatively small. The component Fh is parallel to the turbulence generating structure 2, and thus negligible stress is exerted on the turbulence generating structure 2.

As described above, a turbulence V is generated behind the turbulence generating structure 2 by the current C when an angle of attack A is formed between the turbulence generating structure 2 and the stream line of the current C after colliding with the turbulence generating structure 2. Therefore, the turbulence generating structure 2 may be installed at the stern part of the ship 1 as shown in FIGS. 7 and 7A. In a preferred embodiment of the present invention, the turbulence generating structure 2 is installed on the underwater side surface of the hull 100 between the widest section 120 and the aft end 140 as shown in FIG. 9. Furthermore, as shown in FIG. 11, not only does a boundary layer 31 occur on both sides of the ship 1 while sailing in the water, but also a boundary layer 31 occurs on the bottom surface of the hull 100 (referring to FIGS. 1A and 1B), so that a turbulence generating structure 2 may be also installed on the bottom surface of the ship 1 between the deepest portion 130 and the aft end 140 of the hull 100. In an aspect of the present invention, a plurality of turbulence generating structures may be arranged adjacent to each other with or without a gap in between, and deposed in a linear configuration, such as a line or stripe oblique to the keel line L or other configuration on the surface of hull 100 to fit some particular hull shape, as shown in FIGS. 9 and 10.

FIGS. 4, 5 and 14 respectively illustrate a boundary layer 32 of the laminar flow and a boundary layer 33 of the turbulent flow. The water flow velocity of the interface between the current C and the surface of the hull 100 is zero. The current C is slower near the surface of the hull 100. The length of the arrows in the figures represent velocity. Since the kinetic energy of the water molecule in the turbulent flow is higher, the water molecule with higher kinetic energy tends to relay the kinetic energy to the surface of the hull 100, such that the kinetic energy of the water molecule near the surface of the hull 100 increases, and accordingly increases the flow velocity of current C′. After the turbulence V is formed, the thickness of the turbulent boundary layer 33 is decreased compared with the thickness of the laminar boundary layer 32. Consequently, the drag caused by the current C to the ship 1 becomes correspondingly less.

FIG. 6 and FIG. 7 show a current C flows past the hull 100 of the ship 1. Since the fore end 110 and the aft end 140 of the hull 100 are pointed, the current C1 deflects downwards at the fore part of the hull 100. The current C2 deflects upwards at the aft part of the hull 100 after passing the widest section 120 of the hull 100. As shown in FIG. 7A, when the turbulence generating structure 2 is arranged horizontally, the current C deflects upward at the aft part, which forms an angle of attack A with the impact surface 21 of the turbulence generating structure 2. As a result, the current flow downstream from the turbulence generating structure 2 exhibits turbulence V, so that the drag of the boundary layer 31 on the hull 100 is reduced. The keel line L is the central line between the fore end 110 and the aft end 140 of the hull 100 of the ship 1. The angle A between the impact surface 21 of the turbulence generating structure 2 and the keel line L may be less than 60 degrees. In a preferred embodiment of the present invention, the impact surface 21 of the turbulence generating structure 2 is parallel to the keel line L.

In addition, the turbulence V can increase the pressure on the aft part of the hull 100 and reduce the pressure difference between the fore and aft halves of the hull 100, thereby further reduce the drag caused by the pressure difference on the hull 100 of the ship 1 while sailing.

Referring to FIG. 8, which illustrates the influence of the turbulence generating structure 2 itself after being installed on the surface of the hull 100 of the ship 1. Since the installed direction of the turbulence generating structure 2 is substantially parallel to the keel line L of the ship 1, the normal force F′ of the current C acting on the normal direction of the turbulence generating structure 2 by the current C does not affect the speed of the ship 1, while the tangential force F″ of the current C on the turbulence generating structure acts in a direction that is parallel to the heading of the ship H, so that the resistance of the turbulence generating structure 2 comes from the tangential force F″ and has an extremely small effect on the ship 1.

In an embodiment of the present invention, the hull 100 has a length of 6.246 m, width of 1.057 m, draft of 0.322 m, and the turbulence generating structure 2 is a polyhedron with a length of 2 to 10 cm, width of 0.5 to 2 cm, height of 0.5 to 1 cm. However, the configuration of the turbulence generating structure 2 applied in the present invention is not limited by the above example; the configuration of the turbulence generating structure 2 may be a curved-face rectangle, a slanted-face rectangle, a polygon, a trapezoid, a polyhedron, a triangular solid, a cone, a semi-circular solid or a semi cone as shown in FIG. 12. The dimensions of the turbulence generating structure 2 may be selected as desired in proportion to that of the hull 100.

In the preferred embodiment of the present invention, the turbulence generating structure 2 may be adhered, embedded or welded to the surface of the hull 100, or integrally installed with the hull 100. In the preferred embodiment of the present invention, the range of surface area of the turbulence generating structure 2 are:

2×10⁻² m×0.5×10⁻² m=1×10⁻⁴ m²

10λ10⁻² m×2×10⁻² m=20×10⁻⁴ m²

The surface area of the ship model hull 100 is:

6.246 m×1.057 m=6.6 m²

Accordingly, the range of percentage of the surface area are:

${\frac{1 \times 10^{- 4}\mspace{14mu} m^{2}}{6.6\mspace{14mu} m^{2}} \times 100\%} = {0.0015\%}$ ${\frac{20 \times 10^{- 4}\mspace{14mu} m^{2}}{6.6\mspace{14mu} m^{2}} \times 100\%} = {0.03\%}$

As a result, the surface area of the turbulence generating structure 2 is 0.0015% to 0.03% of the surface area of the ship 1. The material of the turbulence generating structure 2 can be made of metal, plastic, wood, bamboo, glass, ceramic or composite materials.

Referring to FIGS. 13 and 14, FIG. 13 is a schematic diagram of a boundary layer 31 when the current C flows through the hull surface of the ship 1. The velocity of the current C is slower while the current is close to the hull surface and faster while the current is further apart from the hull 100. FIG. 14 is a schematic view of the laminar flow of the boundary layer 32 being fluctuated by the turbulence generating structure 2 becoming the turbulent boundary layer 33. Due to the turbulence generating structure 2 of the present invention being installed on the hull 100, the turbulence occurs after the current C collides with turbulence generating structure 2, and thereby the laminar boundary 32 becomes the thinner turbulent boundary layer 33.

In summary, the present invention can practically achieve the purpose of the invention by providing a turbulence generating structure on the underwater side surface between the widest section and the aft end of the ship, or on the bottom surface between the deepest portion and the aft end of the ship to generate turbulence, and thereby thin the boundary layer and delay the separation to increase the pressure to the stern part of the ship so as to reduce the drag of the ship. Accordingly, the present invention can effectively speed up the ship as well as save the fuel consumption. It is industrially valuable and practically provides a novel improvement for a ship. 

1. A structure for reducing drag of a ship, comprising: a hull, comprising a fore end and an aft end, wherein a keel line is formed between said fore end and said aft end of said hull; and a plurality of turbulence generating structures, provided on a side surface between a widest section and the aft end of said hull, or on a bottom surface between a deepest portion and the aft end of said hull, wherein each turbulence generating structure of the plurality of turbulence generating structures is a polyhedron having a slope or curved front surface and an impact surface, said impact surface has an intersection angle of not more than 60 degrees or parallel with the keel line of the ship, and the surface area of the turbulence generating structure is 0.0015% to 0.03% of the surface area of the ship, wherein the plurality of turbulence generating structures are arranged in one of the following configurations: (a) adjacent to each other with a gap between the turbulence generating structures or (b) without a gap between the turbulence generating structures in a line or stripe oblique to the keel line, whereby the plurality of turbulence generating structures generates turbulence to reduce the drag of the ship while sailing.
 2. The structure for reducing the drag of a ship according to claim 1, wherein a configuration of at least one of the plurality of turbulence generating structures is a curved-face rectangle, a slanted-face rectangle, a polygon, a trapezoid, a polyhedron, a triangular solid, a cone, a semi-circular solid or a semi cone.
 3. The structure for reducing the drag of a ship according to claim 1, wherein at least one of the plurality of turbulence generating structures is adhered, embedded or welded to the surface of the hull, or integrally installed with the hull.
 4. The structure for reducing the drag of a ship according to claim 1, wherein at least one of the plurality of turbulence generating structures is made of metal, plastic, wood, bamboo, glass, ceramic or composite materials. 